Fixed child process signal behaviours. (#128)

* Restored signal handlers upon fork().
* Improved error handling of hpfs process kill scenario.
* Set pgid for forked processes for graceful sending of SIGINT.

src/comm/comm_client.cpp

@@ -62,7 +62,7 @@ namespace comm
         else if (pid == 0)
         {
             // Websocat process.
-            util::unmask_signal();
+            util::fork_detach();
 
             close(write_pipe[1]); //parent write
             close(read_pipe[0]);  //parent read

src/comm/comm_server.cpp

@@ -295,7 +295,7 @@ namespace comm
         else if (pid == 0)
         {
             // Websocketd process.
-            util::unmask_signal();
+            util::fork_detach();
 
             // We are using websocketd forked repo: https://github.com/codetsunami/websocketd
 

src/cons/cons.cpp

@@ -519,7 +519,7 @@ namespace cons
         if (pid == 0)
         {
             // appbill process.
-            util::unmask_signal();
+            util::fork_detach();
 
             // before execution chdir into a valid the latest state data directory that contains an appbill.table
             chdir(conf::ctx.state_rw_dir.c_str());

src/hpfs/hpfs.cpp

@@ -56,7 +56,7 @@ namespace hpfs
         else if (pid == 0)
         {
             // hpfs process.
-            util::unmask_signal();
+            util::fork_detach();
 
             // Fill process args.
             char *execv_args[] = {
@@ -145,7 +145,7 @@ namespace hpfs
         else if (pid == 0)
         {
             // hpfs process.
-            util::unmask_signal();
+            util::fork_detach();
 
             // If the mount dir is not specified, assign a mount dir based on hpfs process id.
             const pid_t self_pid = getpid();

src/main.cpp

@@ -67,12 +67,12 @@ int parse_cmd(int argc, char **argv)
  */
 void deinit()
 {
+    usr::deinit();
+    p2p::deinit();
     cons::deinit();
     state_sync::deinit();
     state_serve::deinit();
     read_req::deinit();
-    usr::deinit();
-    p2p::deinit();
     hpfs::deinit();
 }
 
@@ -190,8 +190,9 @@ int main(int argc, char **argv)
                          << (conf::cfg.startup_mode == conf::OPERATING_MODE::OBSERVER ? "Observer" : "Proposer");
                 LOG_INFO << "Public key: " << conf::cfg.pubkeyhex.substr(2); // Public key without 'ed' prefix.
 
-                if (hpfs::init() != 0 || p2p::init() != 0 || usr::init() != 0 || read_req::init() != 0 ||
-                    state_serve::init() != 0 || state_sync::init() != 0 || cons::init() != 0)
+                if (hpfs::init() != 0 || read_req::init() != 0 ||
+                    state_serve::init() != 0 || state_sync::init() != 0 || cons::init() != 0 ||
+                    p2p::init() != 0 || usr::init() != 0)
                 {
                     deinit();
                     return -1;
@@ -203,7 +204,7 @@ int main(int argc, char **argv)
                 // Wait until consensus thread finishes.
                 cons::wait();
 
-                // deinit() here only gets called when there is an error in consensus. 
+                // deinit() here only gets called when there is an error in consensus.
                 // If not deinit in the sigint handler is called when a SIGINT is received.
                 deinit();
             }

src/sc.cpp

@@ -67,7 +67,7 @@ namespace sc
         else if (pid == 0)
         {
             // Contract process.
-            util::unmask_signal();
+            util::fork_detach();
 
             // Set up the process environment and overlay the contract binary program with execv().
 
@@ -112,7 +112,9 @@ namespace sc
         ret = -1;
 
     success:
-        stop_hpfs_rw_session(ctx);
+        if (stop_hpfs_rw_session(ctx) == -1)
+            ret = -1;
+
         cleanup_fdmap(ctx.userfds);
         if (!ctx.args.readonly)
         {
@@ -131,7 +133,7 @@ namespace sc
     {
         if (pid > 0)
         {
-            int scstatus;
+            int scstatus = 0;
             waitpid(pid, &scstatus, 0);
             if (!WIFEXITED(scstatus))
                 return WEXITSTATUS(scstatus);
@@ -156,17 +158,18 @@ namespace sc
      */
     int stop_hpfs_rw_session(execution_context &ctx)
     {
+        int result = 0;
         // Read the root hash if not in readonly mode.
         if (!ctx.args.readonly && hpfs::get_hash(ctx.args.post_execution_state_hash, ctx.args.state_dir, "/") < 1)
-            return -1;
+            result = -1;
 
         LOG_DEBUG << "Stopping hpfs session... pid:" << ctx.hpfs_pid << (ctx.args.readonly ? " (rdonly)" : "");
 
         if (util::kill_process(ctx.hpfs_pid, true) == -1)
-            return -1;
+            result = -1;
 
         ctx.hpfs_pid = 0;
-        return 0;
+        return result;
     }
 
     /**
@@ -711,9 +714,6 @@ namespace sc
         if (ctx.contract_pid > 0)
             util::kill_process(ctx.contract_pid, true);
 
-        if (ctx.hpfs_pid > 0)
-            util::kill_process(ctx.hpfs_pid, true);
-
         if (ctx.output_fetcher_thread.joinable())
             ctx.output_fetcher_thread.join();
     }

src/util.cpp

@@ -206,13 +206,25 @@ namespace util
         pthread_sigmask(SIG_BLOCK, &mask, NULL);
     }
 
-    // Clears signal mask from the calling thread.
-    // Used for other processes forked from hpcore threads.
-    void unmask_signal()
+    /**
+     * Clears signal mask and signal handlers from the caller.
+     * Called by other processes forked from hpcore threads so they get detatched from
+     * the hpcore signal setup.
+     */
+    void fork_detach()
     {
+        // Restore signal handlers to defaults.
+        signal(SIGINT, SIG_DFL);
+        signal(SIGSEGV, SIG_DFL);
+        signal(SIGABRT, SIG_DFL);
+
+        // Remove any signal masks applied by hpcore.
         sigset_t mask;
         sigemptyset(&mask);
         pthread_sigmask(SIG_SETMASK, &mask, NULL);
+
+        // Set process group id (so the terminal doesn't send kill signals to forked children).
+        setpgrp();
     }
 
     // Kill a process with a signal and if specified, wait until it stops running.

src/util.hpp

@@ -90,7 +90,7 @@ namespace util
 
     void mask_signal();
 
-    void unmask_signal();
+    void fork_detach();
 
     int kill_process(const pid_t pid, const bool wait, const int signal = SIGINT);